Modified, precipitated alumino silicate pigments

ABSTRACT

Novel alkali aluminum silicate particulates, modified with and containing a chemically bound alkaline earth metal, are disclosed. The alumino silicate pigments contain an alkaline earth metal, preferably calcium or magnesium, in addition to an alkali metal, such as sodium. In chemical composition, the pigments contain oxides of the alkaline earth metal, the alkali metal, aluminum and silicon and are distinguishable from co-precipitates. The pigments are prepared by introducing dilute solutions of an alkali silicate and an aluminum salt of a mineral acid into an agitated aqueous receiving medium containing an alkaline earth salt or hydroxide. The pH of the fluid reaction medium may be controlled to form finely divided precipitated particulates having improved properties and which may be used as pigments in paper, paint, rubber, inks, plastics, and the like.

REFERENCE TO COPENDING APPLICATIONS

The present application is a continuation-in-part of U.S. Ser. No.198,022, filed Nov. 5, 1971, and is now allowed U.S. Pat. No. 3,798,046.

BACKGROUND OF THE INVENTION

The present invention relates to finely divided precipitated silicatepigments and, more particularly, to novel modified sodium aluminosilicate pigments which are chemically analagous to zeolites but whichhave certain unique properties and characteristics.

As is well known in the art, natural alkali metal zeolites such asnatrolite and analcine are known to possess water softening propertiesbut have limited usefulness as pigments. In recent years a number ofartificial or synthetic zeolites containing sodium, aluminum and siliconoxides, in various proportions, have been proposed and synthesized.Examples of synthetic zeolites are disclosed in U.S. Pat. Nos.2,882,243; 2,962,335; 2,996,358; 3,010,789; 3,011,869; and 3,012,853. Toa large extent, known synthetic zeolites lack the essentialcharacteristics of pigments and have found limited use in this field.

In this regard, however, there has been developed novel precipitatedsodium alumino silicates that have particular use as pigments in papercoatings, as fillers in rubber compounds, in inks, paints, plastics, andthe like. Such pigments are commercially available and are manufacturedand sold under the trademark "Zeolex" by J. M. Huber Corporation. While"Zeolex" pigments contain the essential oxide components of natural andsynthetic products, these pigments are precipitated products of aluminaand .[.d.]. silica and contain chemically bound sodium and as such arereadily distinguishable from gels and other synthetically producedmaterials. In general, these pigments are precipitated amorphousmaterials and are composed of particles having ultimate sizes of only afew hundredths of a micron in diameter which tend to cling together inclusters of up .Iadd.to .Iaddend.about 1 micron in diameter. In chemicalcomposition, they typically contain Na₂ O and Al₂ O₃ in a molar rationear to 1, as in the range of about 0.8 to 1.2 mols of Na₂ O per mol ofAl₂ O₃ , together with silica which can be present in any of variousselected concentrations ranging from as little as about 2.5 mol to asmuch as about 16 mols of SiO₂ per mol of Al₂ O₃.

As will be discussed in more detail hereinafter, these pigments areadvantageously prepared (see e.g., U.S. Pat. No. 2,739,073) bycomingling dilute solutions of an alkali silicate and an aluminum salt,such as aluminum sulfate. In a preferred embodiment, an amount of waternot greater than about one half of the volume of the solutions to beadded is placed in a suitable reaction vessel provided with a strongagitator. The reactants, i.e., the dilute solutions of the alkalisilicate and an aluminum salt, are then introduced in streams enteringthe water at widely spaced points. In U.S. Pat. No. 2,848,346 suchpigments are prepared by comingling a dilute solution of an alkali and adilute solution of a dispersion containing finely divided silica andaluminum sulfate. The latter is prepared by treating kaolin clay with astrong mineral acid, such as sulfuric acid.

SUMMARY OF THE INVENTION

In summary, the present invention relates to alkaline earth modifiedsodium alumino silicate pigments produced in the manner, and inaccordance with, the teachings of U.S. Ser. No. 198,022, filed Nov. 5,1971. Broadly speaking, the invention covered and disclosed by theaforesaid application, embodies the concept of producing the pigmentsthat are the subject of the present application by a process comprisingintroducing an alkali metal silicate and an aluminum salt into anagitated receiving medium which contains an alkaline earth metal salt,such as magnesium sulfate.

Products produced in this manner, as will be described in more detailhereinafter, contain chemically bound sodium (i.e., the alkali metal) aswell as the chemically bound alkaline earth metal. As such, the productsare readily distinguishable from so-called co-precipitates which containmere mixtures of e.g., an alkali metal alumino silicate and an alkalineearth metal alumino silicate.

.[.it.]. .Iadd.It .Iaddend.is accordingly a general object of thepresent invention to provide a novel synthetic pigment.

Another and more particular object is to provide novel modified aluminosilicate pigments that are especially useful in paper coatings.

Yet another object is to provide alkaline-earth modified sodium aluminosilicate particulates that have particular utility for use in paper, butwhich may be also advantageously employed as reinforcing pigments orfillers in rubber, in inks, paints, plastics, and the like.

The manner in which the foregoing and other objects are achieved inaccordance with the present invention will be better understood in viewof the following detailed description.

DESCRIPTION OF PREFERRED EMBODIMENTS(S)

As noted above, in accordance with the present invention and theteachings of U.S. Ser. No. 198,022, it has been discovered that novelalkaline earth metal modified alkali metal alumino silicate pigments canbe prepared by introducing dilute solutions of an alkali metal silicateand a water soluble salt of aluminum and a strong acid, (such asaluminum sulfate) into an aqueous reaction media containing dispersedtherein an alkaline earth metal salt or hydroxide. As taught in U.S.Ser. No. 198,022, if solutions of the alkali metal silicate and thealuminum sulfate are added to a reaction mass that contains the alkalineearth metal salt or hydroxide, the latter serves as a nucleus ornucleating agent which alters the structure of the resulting modifiedpigment.

The products of the present invention are compositions containingessentially the oxides of an alkaline earth metal, an alkali metal,aluminum and silicon, that may be represented by the general formula

    a X.sub.2 O ·b Al.sub.2 O.sub.3 ·c YO ·d SiO.sub.2 ·e H.sub.2 O

wherein X is an alkali metal such as sodium or potassium and Y is analkaline earth metal. Particularly advantageous results are obtained ifthe alkaline earth metal is magnesium or calcium. The small letters,i.e., a, b, . . . e, represent the mols of the oxides present in thetotal composition. The mol ratio of the constituent oxides may varywidely with the molar ratio of X₂ O to Al₂ O₃ preferably being near to1, such as about 0.8 to 1.4 mols of X₂ O per mol of Al₂ O₃. The mols ofSiO₂ to Al₂ O₃ can be as low as about 2.5 mols up to as much as about 24mols of SiO₂ per mol of Al₂ O₃. The molar ratio of the alkaline earthoxide (YO) to Al₂ O₃ can be varied from about 0.1 to 3, preferably fromabout 1.0 to 1.5. It should be readily understood, however, that achange in the molar ratio of any given two oxides will vary the ratio ofone such oxide to another, i.e., a third oxide in the composition. Tothis end it is more simply stated that the alkaline earth metal salt isadded to the reaction medium in an amount such that the alkaline earthmetal oxide comprises from about 0.1 to 30% of the dry weight of thepigment, based on the particular alkaline earth metal salt used. Forexample, if a magnesium salt is employed, the range of the resulting MgOwould be about 0.1 to 8.0%. With this parameter the other constituentsor reactants, e.g., the alkali metal silicate, can be added in an amountto give the desired molar ratio of X₂ O to Al₂ O₃, etc.

In producing the products of the present invention, and again inaccordance with the method disclosed in U.S. Ser. No. 198,022, thesolutions of the aluminum salt and the alkali metal silicate aremaintained at very low concentrations and under strong agitation duringthe process of comingling and reacting them together in the body of thereaction mass containing the nuclei, i.e., the alkaline earth salt orhydroxide.

In accordance with a first method embodiment, the dilute solutions ofthe reactants are charged slowly into the diluting aqueous mediumcontaining the alkaline earth metal salt and are preferably introducedat widely spaced locations therein. The reaction mass is continuouslyand vigorously stirred or agitated throughout the reaction so as to keepthe dispersion in a fluid condition. The alkali metal silicate solutionsso used should be about 2 molar or lower concentration, and theconcentration of the solution of the aluminum salt should also be about2 molar or lower concentration.

The reaction medium, i.e., the body of water containing the alkalineearth salt, should preferably be about half the combined volumes of thesilicate solution and aluminum salt solution. In this regard, theconcentration of the solutions in the reaction mass should average lessthan about 2.0 molar, depending somewhat upon the particular reactantsemployed, their purity and other variables. Preferably the reactingconcentration is maintained at not more than about 1.0 molar. Thesolutions of the reactants are introduced into the reacting media atwidely spaced points so that a high degree of dilution of each solutionis assured. For example, one solution may be added to the vortex createdby the agitator blade, while the other solution is added near the wallof the vessel. Alternately, the two solutions may be introduced into thereaction vessel at different levels as e.g., one below the surface withthe other being near or above the surface, etc. At the end of thereaction the reaction medium is a fluid mass from which the precipitatedsolid products of the invention may be easily separated.

In general, the addition of the silicate and aluminum salt can bestarted simultaneously or a portion of the silicate can be added priorto the addition of the aluminum salt. The pH of the reaction should bemaintained between about 8 to 12, preferably from between about 8 and10, until all of the alkali silicate has been added. The addition of thealuminum salt solution may then be continued until the .[.ph.]. .Iadd.pH.Iaddend.is reduced to between about 8 and 10.0. While the precipitationof the products of the invention can be executed by the simultaneousaddition of the alkali silicate solution and the aluminum salt solution,it has been found to be particularly advantageous to add a portion ofthe solution of the alkali metal silicate (such as sodium meta ordisilicate) to the receiving medium prior to the introduction of thesolution of the aluminum salt. It is not understood how this affects themechanics of the reaction or precipitating process other than perhapsaffecting the nucleation effect of the alkaline earth metal salt.However products produced in accordance with this second methodembodiment have further improved properties, particularly with regard totheir brightness and their optical properties in paper. In practicingthe latter embodiment, the sodium silicate solution is added to thereaction or receiving media until the pH of the aqueous mass is between8 and 10. Thereafter the solutions of the sodium silicate and thealuminum salt are added simultaneously to the reaction mass until suchtime as the total amount of the aluminum salt solution has been added.After the aluminum salt solution has been added, the addition of thesilicate solution is continued until the pH of the reaction mass isbetween about 8.0 to 10.0.

Upon completion of the reaction procedure, the precipitated pigment isseparated from the reaction liquid usually by filtration, but othermeans of separation, such as centrifuging, can be used. It is preferableto wash the separated pigment with water to remove water soluble saltsand the like. The resulting filter cake is then dried in any suitablemanner. The drying is preferably performed at elevated temperatures withthe temperature of the drying step being used to control the percent ofthe water of the finished pigment. For example, when dried at about 105°C., the pigments usually contain from about 7 to 12 percent water.

It should also be understood that the amount of water remaining in theprecipitated pigment depends upon the time, temperature, and otherconditions of drying. It is not possible to express conditions whichwill be required for drying a particular pigment with any degree ofexactness. This will vary to a large .[.extend.]. .Iadd.extent.Iaddend.,depending e.g., upon the degree of air circulating through the pigment,the type of drying apparatus, etc. As recognized by those skilled in theart, there is a substantial difference in the manner in which "freewater" and "bound water" are held in pigment compositions. Bound waterappears to be chemically combined with the silicate pigment. For thisreason bound water does not readily come off unless dried attemperatures on the order of about 300° C. On the other hand, free watercomes off readily upon drying at relatively moderate temperatures i.e.,up to about 105° C.

As discussed above, the starting materials or reactants employed inproducing the product of the present invention include alkali metalsilicate, the alkaline earth salts or hydroxides and aluminum salts. Asused herein, the term alkali metal silicates includes all the commonforms of alkali metal silicates as, for example, metasilicates,disilicates, and water glass. Water soluble potassium silicates andsodium silicates are particularly advantageous. Because of theirrelatively low cost, sodium silicates are preferred. If employed, sodiumsilicates are effective in any composition in which the mol ratio of theSiO₂ to Na₂ O is from about 1 to 3.3:1.

The aluminum salts preferably include the water soluble acid salts ofaluminum such as aluminum sulfate, aluminum chloride, aluminum nitrateand ammonium alum (aluminum ammonium sulfate). Additionally, thealuminum sulfate solution that is added to the reaction mass maycomprise an aqueous slurry of a finely divided precipitated silicasuspended in a dilute aqueous solution of the salt of aluminum and amineral acid. In this regard, the aqueous reactant solution containingthe pre-precipitated silica in suspension with the solution of thealuminum salt can be obtained by employing finely divided kaolin as abasic raw material and decomposing the kaolin in an aqueous suspensionwith sulfuric acid. The term "kaolin" is used herein to designate kaolinor like clays composed predominately of the mineral kaolinite. Thedecomposition of the kaolin may be carried out in an open vessel if thekaolin has been previously calcined or if uncalcined kaolin is used itshould be reacted with the acid in a closed vessel at pressures on theorder of about 150 to 160 psi as disclosed in U.S. Pat. No. 2,848,346.The product of this decomposition process is essentially a dilutesolution of aluminum sulfate containing very finely divided free silicain suspension.

The alkaline earth salts or hydroxides that may be employed include thesalts of hydroxides of metals from Group 2a of the Periodic Table suchas magnesium, calcium and barium. Preferred salts are the water-solublesalts such as the sulfates, carbonates, nitrates, and chlorides. Howeverothers can be employed. .[.it.]. .Iadd.It .Iaddend.has been found thatthe use of calcium sulfate and magnesium sulfate are particularlyadvantageous and thus are preferred.

As indicated above, the unique pigments of the present invention may beadvantageously employed or used in paper, as reinforcing pigments inrubber compositions, in paints, inks, plastics and the like. Suchpigments may, for example, be employed as reinforcing pigments invarious rubber compositions including natural rubber and syntheticrubber compositions including butadiene 1,3-styrene copolymers,butadiene-acrylonitrile copolymers, butadiene-isobutylene copolymers andlike synthetic elastomers. If employed as rubber pigments of the typedescribed, the alkali silicates should contain from about 1 to about 3.3molar equivalents of SiO₂ per molar equivalent of Na₂ O (when the sodiumsilicate is employed).

While the pigments of the invention may be employed in manyapplications, it has been unexpectedly discovered that the products areparticularly and excellently suited for use in paper. In this regard,pigments produced for paper fillers as described herein should employalkali silicates having SiO₂ in a molar ratio of from about 1.5 to about3.3 to the content of the alkali oxide (Na₂ O). Again preferred resultsare obtained if the mol ratio (SiO₂ /Na₂ O) is from about 2.0 to 2.7.

The following Examples will serve to further illustrate the presentinvention but it is expressly understood that they are not intended tolimit it thereto. The Tables which follow the Examples set forthspecific properties and characteristics of the products of the Examplesnot otherwise included therein. References to Figures are those in U.S.Ser. No. 198,022. As used hereinafter the expression or letters "LOI"refers to loss on ignition, sometimes simply noted as ignition lost. Aswell known in the art, .[.loss.]. .Iadd.lost .Iaddend.on ignition isdetermined by heating a sample of the pigment or product being tested inan oven until the sample maintains a constant weight, that is, nofurther water is driven off upon continued heating. A standard test lossprocedure for establishing ignition loss is TAPPI T-618.

EXAMPLE 1

A dilute alkali silicate solution was prepared by dissolving 4,740 lbs.of sodium silicate (Na₂ O ·2.5 SiO₂) in 2,370 gallons of water. Aseparate dilute solution of aluminum sulfate was prepared by dissolving2,500 lbs. Al₂ (SO₄)₃ ·14H₂ O in 1,000 gallons of water. A 7,500 gal.reaction vessel provided with a propellor type agitator blade wascharged with 1,540 gallons of water to which was added 1,282 lbs. ofMgSO₄ ·7 H₂ O, and the agitator was started. The sodium silicatesolution was charged to the reaction vessel at a rate of 46.5 GPM as athin stream directly into the vortex formed by the rotating agitatorblade. The addition of the sodium silicate solution was continued for aperiod of 16 minutes at the end of which time the pH of the reactionmass was 9.9. Thereafter, and with the silicate solution still beingintroduced, the aluminum sulfate solution was introduced at a rate of25.1 GPM for an additional period of 35 minutes. The pH, during thesimultaneous addition of the silicate solution and the aluminum salt,was reduced to about 9.5. At the end of the 51 minute reaction periodall the silicate solution had been added. Thereafter the addition of thealuminum sulfate solution was continued until the final pH of thereaction mass was 8.8. This required an additional 5.0 minutes. Thetemperature of the solutions of the reactants introduced into thereaction vessel as well as the receiving medium was maintained at about65° C. throughout the reaction. After the pH of the reaction mass wasreduced to 8.8 and all of the aluminum salt had been added, agitation ofthe reaction mass was continued for an additional 15 minutes. Theprecipitate was then separated by filtration and thoroughly washed withwater at ambient temperatures. The resulting filter cake was dried at110° C. The cake was pulverized in a hammer mill. The material soproduced was a finely divided white particulate made up of particlesless than 0.05 microns in diameter. The specific gravity of the productwas 2.2. The pour density was 9.5 lbs. per cubic foot and the producthad a BET surface area of 97m² /g. From a chemical analysis of theproduct the following formula was calculated:

    1.3 Na.sub.2 O·1.0 Al.sub.2 O.sub.3 ·1.2 MgO·14.3 SiO.sub.2 ·4.3 H.sub.2 O

EXAMPLE 2

The procedure of Example 1 was repeated except that the sodium silicateemployed contained 1.4, 1.83, 2.34, 2.8, and 3.35 mols of SiO₂ per molof Na₂ O respectively. The products obtained in this Example possessedproperties similar to those of product of Example 1.

EXAMPLE 3

The general procedure of Example 1 was repeated except that magnesiumchloride, magnesium hydroxide, and magnesium nitrate, were substitutedfor the magnesium sulfate of Example 1. The products obtained weresubstantially the same as that in Example 1.

EXAMPLE 4

The general procedure of Example 1 was repeated except that the aluminumsulfate and sodium silicate solutions were added simultaneously at theoutset of the reaction or precipitation process. In addition the pH ofthe reaction mass was maintained constant (8.0) by adjusting the rate ofaddition of the two solutions. At the end of the reaction period, whichrequired 51 minutes, the final pH of the slurry was increased to 9.5 bythe addition of a dilute solution of the silicate. This required anadditional 3 minutes. The product produced in this Example wassubstantially the same as the product of Example 1.

EXAMPLE 5

The general procedure of Example 1 was repeated except that aluminumchloride, aluminum nitrate and ammonium alum were substitued for thealuminum sulfate employed in Example 1. The products produced weresubstantially the same as that of Example 1.

EXAMPLE 6

The general procedure of Example 1 was repeated except that in a seriesof two test runs the reaction vessel was charged with 1,480 gallons ofwater to which was added 1,081 lbs. of calcium sulfate and 1,053 lbs. ofcalcium carbonate, respectively. After the precipitate was recovered byfiltration, washed and dried, the product from test run No. 2 wasreslurried and treated with sufficient HCl to reduce the pH of theslurry to about 3.5.Iadd.. .Iaddend.Thereafter sufficient NaOH was addedto the pigment slurry to increase the slurry pH to 8.8. The productsobtained both prior to and after the additional treatment with NaOHpossessed properties similar to that of the products of Example 1. In aseries of further tests the above general procedure was repeated exceptthat the amount of the calcium salt was varied and sodium silicate wassubstituted for the NaOH. (See Table 3 below).

EXAMPLE 7

The procedure of Example 1 was repeated except that the aluminum sulfatesolution consisted of a slurry of finely divided precipitated silica ina solution of aluminum sulfate that was prepared by reacting 3250 lbs.of commercial kaolin with 4000 lbs. of 95% sulfuric acid in 1,000gallons of water. The slurry was formed by agitating the kaolin with thesulfuric acid in a lead .[.line.]. .Iadd.lined .Iaddend.autoclave at atemperature of 185° C. for 10 hours. This reaction mass as cooled,discharged and made up to volume of 3,000 gallons by the addition ofwater. In examination, the finely divided precipitated silica particlessuspended in the aqueous solution of aluminum sulfate showed that almostall the precipitated silica particles were less than 0.2 microns in itsgreatest dimension. The separate dilute solution of the sodium silicateand the aluminum sulfate solution containing the finely dividedprecipitate silica was then charged to the reaction vessel in the mannerof Example 1. The precipitate was recovered by filtration with water anddried at 110° C. The filter cake was obtained in the form of soft lumps.On passing these lumps through the hammer mill a white powder wasobtained, substantially all the particles of which were smaller than 0.5microns in their greatest diameter.

EXAMPLE 8

The procedure of Example 1 was repeated except that the reaction vesselwas charged with 1,500 gallons of water to which was added 1,085 lbs. ofbarium sulfate. The product produced in this Example was substantiallythe same as that of Example 1.

EXAMPLE 9

The procedure of Example 1 was repeated except that a mixture of MgSO₄·7 H₂ O and CaCO₃ (641 lbs. each or a total of 1,282 lbs.) was chargedto the reaction vessel containing 1,540 gallons of water. The generalproperties of the product produced in this Example (e.g., particle size,surface area, density, etc.) were similar to those of the product ofExample 1. Further properties of the pigment are shown in the Table setforth hereinbelow.

EXAMPLE 10

The general procedure of Example 1 as used to prepare 7 batches undervaried reaction pH ranges. .[.FIG. 5 shows the reaction pH ranges underwhich these batches were precipitated..]. These Examples clearlyestablish the flexibility of the method of the invention to produce agiven product consistently. Table 4 shows the effect of these variationson the physical properties of the product. Table 5 illustrates the finepaper properties of the products produced in accordance with thisExample.

EXAMPLE 11

The general procedure of Example 1 was repeated except that the amountof the MgSO₄ added to the receiving medium was varied (See Table 2below) such that the final product contained varying amounts ofmagnesium based on the dry weight of the product.

EXAMPLE 12

In this Example, the procedure of Example 2 of U.S. Pat. No. 2,739,073was duplicated and the resulting pigment recovered. Comparative data ofthe properties of this pigment (fine paper properties) and that of thepigment produced in accordance with Examples 1-11, is shown in Tables 2and 3 (with the pigment produced by way of Example 2 of the patent beingidentified as "Zeolex 23").

EXAMPLE 13

In this Example, the procedure of Example 3 of U.S. Pat. No. 2,739,073was duplicated. The resulting pigment product was recovered. Comparativedata of the properties of this pigment and that of the pigment producedin accordance with Examples 1-11 is shown in the following Tables withthe product of Example 3 of the said patent being identified as "Zeolex20."

EXAMPLE 14

The procedure of Example 3 of U.S. Pat. No. 2,739,073 was duplicatedexcept that MgSO₄ was substituted for the calcium hydroxide. It wasfound that this product had properties substantially the same as theproduct produced by Example 3 of U.S. Pat. No. 2,739,073 (see Example 13above) with comparative data for the two pigments with that of theproduct produced in accordance with Examples 1-11 also beingsubstantially the same. At this point it may be noted that in Example 3of U.S. Pat. No. 2,739,073, the percent of the calcium hydroxideemployed therein is 5% Ca (7.5% CaO). In a series of further tests, theprocedures of Example 3 of this patent (see Example 13 above) wasrepeated except that the amount of the calcium hydroxide employed wasvaried so that the amount of calcium oxide present in the product was

                                      TABLE 1                                     __________________________________________________________________________    CHEMICAL-PHYSICAL PROPERTIES OF PIGMENTS MODIFIED WITH MAGNESIUM AND          CALCIUM                                                                                       Pigment          Valley                                                                             Oil   .Iadd. lbs./ft.sup.3.Iaddend.                                                 6         BET                                     (Elrepho) 20%                                                                              % 325                                                                             Abrasion                                                                           Absorption                                                                          Density, .[.No./ft.sup.3                                                                Surface                 Pigment         Brightness                                                                          % LOI                                                                             pH Residue                                                                           mg loss                                                                            cc/100 g                                                                            Pour Pack Area                    __________________________________________________________________________    Example 1                                                                           MgSO.sub.4                                                                              90.8  7.0 11.3                                                                             4.4 6.2  132   10.0 20.9  97                     Example 2                                                                           MgSO.sub.4                                                                              91.6  8.1 10.9                                                                             3.7 2.7  140   8.6  18.3 114                     Example 2                                                                           MgSO.sub.4                                                                              91.6  8.1 11.4                                                                             5.1 5.5  156   10.0 21.6 106                     Example 2                                                                           MgSO.sub.4                                                                              91.0  7.6 11.2                                                                             3.6 10.9 135   10.4 22.4 102                     Example 2                                                                           MgSO.sub.4                                                                              91.1  7.5 11.3                                                                             4.8 7.5  140   10.0 17.5 122                     Example 2                                                                           MgSO.sub.4                                                                              91.7  8.0 11.3                                                                             0.9 8.0  136   10.8 22.0 105                     Example 3                                                                           MgCl.sub.2                                                                              90.4  9.7 10.6                                                                             0.8 4.3  138   10.2 20.1 142                     Example 3                                                                           Mg(OH).sub.2                                                                            90.8  9.2 10.4                                                                             2.4 7.8  131   10.2 22.3 142                     Example 3                                                                           MgNO.sub.3                                                                              91.0  9.6 10.1                                                                             1.8 6.8  135   12.0 25.0 176                     Example 4                                                                           MgSO.sub.4                                                                              91.3  8.1 11.0                                                                             5.3 6.6  148   9.2  20.1 119                     Example 6                                                                           CaSO.sub.4                                                                              90.8  8.5 11.3                                                                             1.25                                                                              6.0  132   10.1 20.8 105                     Example 6                                                                           CaCO.sub.3                                                                              91.0  9.3 10.9                                                                             0.81                                                                              8.0  170   9.9  22.0 111                     Example 8                                                                           BaSO.sub.4                                                                              91.2  9.0 11.3                                                                             1.01                                                                              6.5  160   10.2 23.2 112                     Example 9                                                                           MgSO.sub.4 & CaCO.sub.3                                                                 91.4  8.9 11.0                                                                             1.04                                                                              7.5  156   10.4 20.4 130                     __________________________________________________________________________     from about 0.1 to 8% based on the dry weight of the composition. The     resulting pigments had substantially the same properties as the pigment     produced in accordance with Example 3 of the said patent. This was also     found to be true when varying the amounts of MgSO.sub.4 substituted for     the calcium salt as set forth in this Example.

                                      TABLE 2                                     __________________________________________________________________________    FINE PAPER PROPERTIES OF PIGMENTS MODIFIED WITH MAGNESIUM                                        % Solids                                                                           % F                                                                 % Mg in                                                                            of Wet                                                                             I  % Pigment                                                                           TAPPI TAPPI                                  Pigment       Pigment                                                                            Cake L  Retention                                                                           Brightness                                                                          Opacity                                __________________________________________________________________________    Unfilled                -- --    87.0  80.0                                   Zeolex 23-Control                                                             Example 11    None 28.4 3  56    88.0  81.2                                                           6  52    88.3  82.1                                                           9  50    88.9  83.0                                   Example 11    0.43 26.4 3  49    88.0  81.6                                                           6  53    88.6  82.9                                                           9  50    89.3  83.8                                   Example 11    0.49 27.5 3  48    87.9  81.6                                                           6  45    88.5  83.0                                                           9  42    88.9  83.9                                   Example 11    0.43 29.3 3  48    88.0  81.6                                                           6  53    88.8  83.1                                                           9  50    89.0  84.1                                   Example 11    0.55 26.4 3  57    88.0  81.5                                                           6  52    88.6  82.7                                                           9  49    89.0  83.6                                   Example 11    0.56 29.7 3  51    88.2  81.6                                                           6  47    88.9  82.9                                                           9  44    89.3  83.9                                                           -- --    88.4  79.3                                   Example 11    1.5  28.7 3  53    88.9  81.6                                                           6  51    89.3  83.2                                                           9  52    89.5  84.0                                   Example 11    3.3  24.0 3  48    88.9  81.7                                                           6  46    89.3  83.6                                                           9  48    89.5  84.9                                   Example 11    2.7  26.0 3  48    89.0  81.2                                                           6  47    89.5  82.8                                                           9  47    89.8  83.8                                   Example 11    2.7  24.1 3  44    89.0  81.5                                                           6  42    89.5  82.9                                                           9  47    89.7  83.5                                   Example 11    1.8  27.3 3  44    89.2  81.0                                   (Note: in this test, pigment                                                                          6  44    89.8  83.3                                   reslurried and treated in                                                                             9  42    90.2  84.2                                   accordance with Example 6)                                                    Example 11    8.0  26.6 .[.8.]..Iadd.3.Iaddend.                                                          45    89.2  81.7                                                           6  44    89.6  83.7                                                           9  42    90.0  84.9                                   __________________________________________________________________________

                  TABLE 3                                                         ______________________________________                                        FINE PAPER PROPERTIES OF                                                      PIGMENTS MODIFIED WITH CALCIUM AND BARIUM                                                      %       %   %                                                                 Solids  F   Pigment                                                                              TAPPI                                             % Ca in  of Wet  I   Reten- Bright-                                                                             TAPPI                               Pigment Pigment  Cake    L   tion   ness  Opacity                             ______________________________________                                        Un-                      --  --     88.0  80.3                                filled                                                                        Zeolex 23                                                                             None     28.6    3   55     88.7  82.0                                (Control)                6   53     89.0  82.5                                                         9   52     89.2  84.3                                Example 0.4      24.3    3   52     88.7  82.2                                (CaSO.sub.4)             6   57     89.1  83.7                                                         9   56     89.4  84.7                                Example  0.55    23.6    3   47     88.9  82.1                                6                                                                             (CaSO.sub.4)             6   49     89.1  83.6                                                         9   46     89.4  84.7                                Example 4.1      25.4    3   47     89.2  82.0                                6                                                                             (CaSO.sub.4)             6   49     89.4  83.4                                                         9   47     89.7  84.6                                Example 4.3      25.2    3   47     89.2  82.0                                6                                                                             (CaCO.sub.3)             6   49     89.4  83.3                                                         9   47     89.7  84.4                                Example 4.6      28.8    3   47     89.6  82.4                                6                                                                             (CaSO.sub.4)             6   49     89.9  84.1                                                         9   46     89.9  85.5                                Example 3.9      29.0    3   47     89.1  82.2                                6                                                                             (CaCO.sub.3)             6   47     89.4  83.8                                                         9   46     89.6  85.1                                        % Ba in                                                                       Pigment                                                               Example 4.0      28.7    3   46     89.1  82.2                                8                                                                             (BaSO.sub.4)             6   49     89.4  84.0                                                         9   46     89.6  86.3                                ______________________________________                                    

                                      TABLE 4                                     __________________________________________________________________________    PHYSICAL PROPERTIES AND REACTION CONDITIONS OF PIGMENTS MODIFIED              WITH MAGNESIUM IN ACCORDANCE WITH EXAMPLE 10                                     Min.           Valley                                                                             % 325                                                                             BET Sur                                                                            Oil                                           Run                                                                              Excess                                                                            Prec. pH                                                                           Final                                                                            %  Abrasion                                                                           screen                                                                            face area                                                                          Absorption                                                                          Pigment                                 No.                                                                              Silicate                                                                          Range                                                                              pH LOI                                                                              mg-loss                                                                            residue                                                                           m.sup.2 /g                                                                         cc/100 g                                                                            Brightness                              __________________________________________________________________________    1  16  10.0-10.0                                                                          8.8                                                                              6.52                                                                             4.5  0.24                                                                              110   112  93.3                                    2  16  10.0-9.0                                                                           8.8                                                                              6.81                                                                             5.6  0.16                                                                              101  110   93.5                                    3  16  10.0-9.0                                                                           8.8                                                                              6.53                                                                             6.5  0.12                                                                               71  108   93.3                                    4  20  10.5-10.5                                                                          8.8                                                                              6.42                                                                             5.6  0.48                                                                              124  118   92.7                                    5  20  10.5-9.5                                                                           8.8                                                                              6.43                                                                             4.2  0.12                                                                              108  120   93.3                                    6  20  10.5-9.5                                                                           8.8                                                                              6.55                                                                             2.9  0.14                                                                               82  110   93.5                                    7   6  8.0-8.0                                                                            9.8                                                                              7.06                                                                             4.1  0.06                                                                               75  137   94.5                                    8   6  8.0-9.0                                                                            9.8                                                                              6.38                                                                             2.9  0.04                                                                               59  127   94.1                                    9   6  8.0-9.8                                                                            9.8                                                                              6.56                                                                             1.5  0.10                                                                               61  136   93.2                                    __________________________________________________________________________

                                      TABLE 5                                     __________________________________________________________________________    FINE PAPER PROPERTIES OF DRIED AND MILLED MAGNESIUM MODIFIED SILICATE         PIGMENTS PRODUCED IN ACCORDANCE WITH EXAMPLE 10                                    Minutes                        Pigments                                  Run  Excess                                                                             Prec. pH                                                                           Final                                                                            %    % Pigments                                                                           Tappi Tappi                                     No.  Silicate                                                                           Range                                                                              pH Filler                                                                             Retention                                                                            Brightness                                                                          Opacity                                   __________________________________________________________________________    Control           unfilled    85.6  82.0                                      1    16   10.0-10.0                                                                          8.8                                                                              3    50     87.1  85.0                                                        6    49     87.9  87.0                                                        9    48     88.5  88.3                                      2    16   10.0-9.0                                                                           8.8                                                                              3    51     87.1  85.0                                                        6    51     87.9  87.2                                                        9    50     88.5  88.5                                      3    16   10.0-9.0                                                                           8.8                                                                              3    51     87.1  85.0                                                        6    52     87.9  87.2                                                        9    52     88.6  88.6                                      4    20   10.5-10.5                                                                          8.8                                                                              3    50     87.1  84.8                                                        6    50     87.9  86.9                                                        9    47     88.5  88.2                                      5    20   10.5-9.5                                                                           8.8                                                                              3    50     87.1  84.8                                                        6    50     87.9  86.9                                                        9    48     88.5  88.1                                      6    20   10.5-9.5                                                                           8.8                                                                              3    48     87.1  85.0                                                        6    47     88.0  87.1                                                        9    50     88.6  88.5                                      7    6    8.0-8.0                                                                            9.8                                                                              3    50     87.3  85.4                                                        6    49     88.3  87.6                                                        9    50     89.1  89.0                                      8    6    8.0-9.0                                                                            9.8                                                                              3    50     87.3  85.4                                                        6    48     88.3  87.6                                                        9    50     89.0  89.0                                      9    6    8.0-9.8                                                                            9.8                                                                              3    49     87.1  85.2                                                        6    48     88.0  87.3                                                        9    49     88.6  88.7                                      __________________________________________________________________________

                  TABLE 6                                                         ______________________________________                                        PHYSICAL PROPERTIES OF THE PRODUCT OF THE                                     INVENTION AND THE PRIOR ART                                                   .[.Product of Invention  Prior Art.].                                                             .Iadd.Product of                                                                         Prior Art                                                          Invention.Iaddend.                                                                       (Zeolex 20)                                                        (Example 10.                                                                             (Example                                       Properties          (Run 2)    13)                                            ______________________________________                                        20% pH              9.9        10.4                                           % LOI               7.7-8.5    12.6                                           Alkalinity meg/100 g                                                                              44         148                                            Oil .Iadd.Absorption.Iaddend..[.Adsorption.]. cc/100g                                             126        140                                            BET Surface Area M.sup.2 /g                                                                       54         72                                             % 325 Screen Residue                                                                              0.02-0.06  8.0-10.0                                       ______________________________________                                         NOTE:                                                                         From further tests it was found that the product of the invention (as per     Examples 1-11) had the following range of properties: 20% pH  8.5 to 10;%     LOI  6 to 8.5; alkalinity (meg/100 g)  40 to 60; oil adsorption (cc/100 g      100 .Iadd.to 145; BET surface area.Iaddend.(M.sup.2 /g)  50 to 120; and      %325 screen Residue  .02 to .06. This combination of properties is unique     and could not be reproduced following the teachings and examples of U.S.      2,739,073. The product of the invention has a lower pH and alkalinity.        This is believed to be due to the manner in which the alkaline earth meta     is bound to the pigment. The LOI shows, e.g. a difference in the amount o     bound water.                                                             

                                      TABLE 7                                     __________________________________________________________________________    COMPARATIVE DATA-FINE PAPER PROPERTIES                                                                       TAPPI TAPPI                                                 % Alkaline                                                                          %    % Pigment                                                                            BRIGHT-                                                                             OPACI-                                   Pigment      EARTH FILLER                                                                             RETAINED                                                                             NESS  TY                                       __________________________________________________________________________    Unfilled     0     --   --     85.9  82.1                                     Zeolex 23 (Control)                                                                        0     3    40     87.1  85.3                                     Example 2-U.S. 2,739,073                                                                         6    40     87.9  87.4                                                        9    39     88.6  88.2                                     Zeolex 20    5% Ca 3    53     86.5  83.4                                     Example 3-U.S. 2,739,073                                                                         6    50     86.9  84.4                                                        9    47     87.1  85.0                                     Zeolex 20 (Mg)                                                                             5% Mg 3    50     86.6  83.1                                     Example 14 of Application                                                                        6    50     87.0  83.8                                                        9    49     87.3  84.3                                     Product of Example 10                                                                      3%    3    47     87.6  87.6                                     (Run 8)            6    46     88.7  88.7                                                        9    48     89.5  89.5                                     Product of Example 6                                                                       3%    3    47     87.4  85.2                                                        6    48     88.1  87.0                                                        9    49     89.0  88.2                                     Product of Example 8                                                                       3%    3    48     87.2  85.4                                                        6    48     87.9  87.3                                                        9    49     88.8  88.5                                     __________________________________________________________________________

To further illustrate the uniqueness of the pigment of the inventionwith that of the prior art, the pigment of the invention was tested in arubber formulation, shown in Table 8 below, and compared with anidentical formulation except that the pigment employed was that producedin accordance with Example 3 of U.S. Pat. No. 2,739,073 (see Example 13above).

Tests on the rubber formulation included the following: A. HardnessData--Olsen Test pieces 8-12 at 320° F.; B. Abrasion Data--NBS 8-12 at320° F.; C. Olsen Stiffness on Unaged Ross Flex pieces, 8 inch lbs., 4inch Span, 8-12 at 320° F.; and D. Rheometer Data: (1) 320° F. (2) HiSpeed. (3) 30 .[.foot.]. .Iadd.minute .Iaddend.Chart Motor. (4) Range100. (5) Preheat 60 Secs. (6) 3° Arc.

                  TABLE 8                                                         ______________________________________                                        Ingredients      Parts/100 RHC                                                ______________________________________                                        SBR 1502         100.0                                                        Pliolite S6B     20.0                                                         Zinc Oxide       3.0                                                          Stearic Acid     2.0                                                          Cumar MH 21/2    7.5                                                          Pigment (Ex. 11, 1.5% Mg)                                                                      66.5                                                         Santocure        2.0                                                          DOTG             1.0                                                          Sulfur           2.5                                                          Total            204.5        Sp.Gr. 1.215                                    ______________________________________                                    

The results of the test established when the pigment produced as perExample 3 of U.S. Pat. No. 2,739,037 was employed, the rubberformulation cured too fast resulting in a hard, stiff rubber with poorabrasion resistance. On the other hand, the pigment of the inventionproduced good rubber reinforcing with high abrasion resistance,increased modulus, tensile strength and elongation. The Olsen stiffnesswas 100 (8 .[.inch.]. .Iadd.minute .Iaddend.cure) for the pigment of theinvention vs. 187 and 191 (6 .[.foot.]. .Iadd.minute .Iaddend.and 8.[.foot.]. .Iadd.minute .Iaddend.respectively) for the pigment of theprior art. The NBS abrasion was 100 vs 67 and 65 for the same curerates. A further summary of the tests is shown in Table 9.

                                      TABLE 9                                     __________________________________________________________________________           Cure                                                                             200% 300% Tear Data                                                 Pigment                                                                              Min.                                                                             Modulus                                                                            Modulus                                                                            Tensile                                                                           Elongation                                                                          Longitudinal                                                                         Transverse                                                                          Average                            __________________________________________________________________________    Example 11                                                                           6  950  1275 2033                                                                              500   267    279   273                                (1.5% Mg)                                                                            8  1008 1342 1950                                                                              467   278    266   272                                       12 983  1317 1883                                                                              467   270    273   272                                Example 3 of                                                                         4  858  1092 1717                                                                              477   266    285   276                                U.S. 2,739,073                                                                       6  850  1075 1675                                                                              567   263    270   267                                (Prior Art)                                                                          10 892  1150 1642                                                                              433   265    265   265                                __________________________________________________________________________     Note:                                                                         Test pieces employing pigment of Example 3 (U.S. 2,739,073) were cured fo     6 and 10 minutes to achieve the same degree of cure as 8 and 12 minute        cures when pigment of invention is employed.                             

What is claimed is: .[.1. A finely divided, precipitated, white powderycomposition comprising chemically bound oxides of magnesium, sodium,aluminum, and silicon in a uniform matrix substantially all of theparticles of which are less than 1 micron in diameter, the molar ratioof SiO₂ to Na₂ O being at least about 4 to 1 and the molar ratio of Na₂O to Al₂ O₃ being from about 0.8 to 1.4:1, said magnesium oxide beingpresent in an amount of from about 0.1 to 8 percent based on the dryweight of the composition; said composition having a specific gravity of2.0 to 2.4; said composition further having an alkalinity in the rangeof from about 40-60 meg/100 g; a LOI in the range of from about 6-8.5%by weight; an oil absorption in the range of from about 110 to 145cc/100 g and a surface area in the range of from about 50 to 120 M²/g..]. .[.2. A finely divided precipitated, white powdery compositioncomprising chemically bound oxides of calcium, sodium, aluminum, andsilicon in a uniform matrix substantially all of the particles of whichare less than 1 micron in diameter, the molar ratio of SiO₂ to Na₂ Obeing at least about 4 to 1 and the molar ratio of Na₂ O to Al₂ O₃ beingfrom about 0.8 to 1.4:1, said calcium being present in an amount of fromabout 0.1 to 8 percent based on the dry weight of the composition havinga specific gravity of 2.0 to 2.4; said composition further having analkalinity in the range of from about 40-60 meg/100 g; a LOI in therange of from about 6-8.5% by weight; an oil absorption in the range offrom about 110 to 145 cc/100 g and a surface area in the range of fromabout 50 to 120 M² /g..]. .[.3. A finely divided, precipitated, whitepowdery composition comprising chemically bound oxides of barium,sodium, aluminum, and silicon in a uniform matrix substantially all ofthe particles of which are less than 1 micron in diameter, the molarratio of SiO₂ to Na₂ O being at least about 4 to 1 and the molar ratioof Na₂ O to Al₂ O₃ being from about 0.8 to 1.4:1, said barium beingpresent in an amount of from about 0.1 to 8 percent based on the dryweight of the composition having a specific gravity of 2.0 to 2.4; saidcomposition further having an alkalinity in the range of from about40-60 meg/100 g; a LOI in the range of from about 6-8.5% by weight; anoil absorption in the range of from about 110 to 145 cc/100 g and asurface area in the range of from about 50 to 120 M² /g..]. .[.4. Thecomposition in accordance with claim 1, said composition furthercomprising the oxides of magnesium, sodium, aluminum, and siliconprecipitated in intimate association with finely divided particles ofprecipitated silica..]. .[.5. The composition in accordance with claim2, said composition further comprising the oxides of calcium, sodium,aluminum, and silicon precipitated in intimate association with finelydivided particles of pre-precipitated silica..]. .[.6. The compositionin accordance with claim 3, said composition further comprising theoxides of barium, sodium, aluminum, and silicon precipitated in intimateassociation with finely divided particles of pre-precipitated silica..]..Iadd.
 7. A finely divided precipitated, white powdery compositioncomprising chemically bound oxides of an alkaline earth metal selectedfrom the group consisting of magnesium, calcium, barium, or combinationsthereof; sodium; aluminum; and silicon in a uniform matrix substantiallyall of the particles of which are less than 1 micron in diameter, themolar ratio of SiO₂ to Na₂ 78 O being at least about 4 to 1 and themolar ratio of Na₂ O to Al₂ O₃ being from about 0.8 to 1.4:1, saidalkaline earth metal oxide being present in an amount of from about 0.1to 8 percent based on the dry weight of the composition having aspecific gravity of 2.0 to 2.4; said composition further having a LOI inthe range of from about 6.38 to 9.7% by weight; an oil absorption in therange of from about 108 to 170 cc/100 g and a surface area in the rangeof from about 59 to 176 M² /g. .Iaddend..Iadd.
 8. The composition inaccordance with claim 7, said composition further comprising the oxidesof an alkaline earth metal, sodium, aluminum, and silicon precipitatedin intimate association with finely divided particles ofpre-precipitated silicate. .Iaddend..Iadd.
 9. The composition of claim 7wherein said alkaline earth metal is magnesium. .Iaddend..Iadd.
 10. Thecomposition of claim 9 wherein said composition has an oil absorption inthe range of from about 108 to 156 cc/100 g. .Iadd.
 11. The compositionof claim 7 wherein said alkaline earth metal is calcium. .Iadd.
 12. Thecomposition of claim 11 wherein said composition has a LOI in the rangeof about 8.5 to 9.3% by weight. .Iaddend..Iadd.
 13. The composition ofclaim 12 wherein said composition has an oil absorption in the range offrom about 132 to 170 cc/100 g. .Iaddend..Iadd.
 14. The composition ofclaim 13 wherein said composition has a surface area in the range offrom about 105 to 111 M² /g. .Iaddend..Iadd.
 15. The composition ofclaim 7 wherein said alkaline earth metal is barium. .Iaddend..Iadd. 16.The composition of claim 15 wherein said composition has a LOI of about9.0% by weight. .Iaddend..Iadd.
 17. The composition of claim 16 whereinsaid composition has an oil absorption in the range of about 160 cc/100g. .Iaddend..Iadd.
 18. The composition of claim 17 wherein saidcomposition has a surface area of about 112 M² /g. .Iaddend..Iadd. 19.The composition of claim 7 wherein said alkaline earth metal is acombination of magnesium and calcium. .Iaddend..Iadd.
 20. Thecomposition of claim 19 wherein said composition has a LOI of about 8.9%by weight. .Iaddend..Iadd.
 21. The composition of claim 20 wherein saidcomposition has an oil absorption of about 156 cc/100 g. .Iaddend..Iadd.22. The composition of claim 21 wherein said composition has a surfacearea of about 130 M² /g. .Iaddend. .Iadd.
 23. A finely dividedprecipitated, white powdery composition comprising chemically boundoxides of an alkaline earth metal selected from the group consisting ofmagnesium, calcium, barium, or combinations thereof; sodium; aluminum;and silicon in a uniform matrix substantially all of the particles ofwhich are less than 1 micron in diameter, the molar ratio of SiO₂ to Na₂O being at least about 4 to 1 and the molar ratio of Na₂ O to Al₂ O₃being from about 0.8 to 1.4:1, said alkaline earth metal oxide beingpresent in an amount of from about 0.1 to 8 percent based on the dryweight of the composition having a specific gravity of 2.0 to 2.4..Iaddend..Iadd.
 24. The composition of claim 23 wherein said alkalineearth metal is magnesium. .Iaddend..Iadd.
 25. The composition of claim23 wherein said alkaline earth metal is calcium. .Iaddend..Iadd.
 26. Thecomposition of claim 23 wherein said alkaline earth metal is barium..Iaddend..Iadd.
 27. The composition of claim 23 wherein said alkalineearth metal is a combination of magnesium and calcium. .Iaddend..Iadd.28. The composition of claim 23 wherein said composition has a LOI inthe range of from about 6.38 to 9.7% by weight. .Iaddend..Iadd.
 29. Thecomposition of claim 25 wherein said composition has a LOI in the rangeof about 8.5 to 9.3% by weight. .Iaddend..Iadd.
 30. The composition ofclaim 23 wherein said composition has an oil absorption in the range offrom about 108 to 170 cc/100 g. .Iaddend..Iadd.
 31. The composition ofclaim 24 wherein said composition has an oil absorption in the range offrom about 108 to 156 cc/100 g. .Iaddend. .Iadd.
 32. The composition ofclaim 25 wherein said composition has an oil absorption in the range offrom about 132 to 170 cc/100 g. .Iaddend..Iadd.
 33. The composition ofclaim 23 wherein said composition has a surface area of from about 59 to176 M² /g. .Iaddend..Iadd.
 34. The composition of claim 25 wherein saidcomposition has a surface area in the range of from about 105 to 111 M²/g. .Iaddend..Iadd.
 35. The composition of claim 23 wherein saidcomposition has a pigment (Elrepho) brightness of from about 90.4 to94.5. .Iaddend..Iadd.
 36. The composition of claim 23 wherein saidcomposition has a 20% pH of from about 10.1 to 11.3. .Iaddend..Iadd. 37.The composition of claim 23 wherein said composition has a 325 screenresidue of from about 0.04 to 5.3%. .Iaddend..Iadd.
 38. The compositionof claim 23 wherein said composition has a Valley Abrasion of from about1.5 to 10.9 mg. loss. .Iaddend..Iadd.
 39. The composition of claim 23wherein said composition has a pour density of from about 8.6 to 12.0lb./ft³. .Iaddend. .Iadd.
 40. The composition of claim 23 wherein saidcomposition has a pack density of from about 17.5 to 25.0 lb./ft³..Iaddend..Iadd.
 41. The composition of claim 23 wherein said compositionhas a percentage retention in fine paper of from about 42 to 57%..Iaddend..Iadd.
 42. The composition of claim 23 wherein said compositionhas a percentage of solids in its wet cake of from about 23.6 to 29.7%solids. .Iaddend..Iadd.
 43. The composition of claim 23 wherein saidcomposition has a TAPPI Brightness in fine paper of from about 87.1 to90.2. .Iaddend. .Iadd.
 44. The composition of claim 23 wherein saidcomposition has a TAPPI Opacity in fine paper of from about 79.3 to89.0. .Iaddend..Iadd.
 45. The composition of claim 23 wherein saidcomposition consists essentially of particles substantially all of whichare less than 0.5 microns in diameter after milling. .Iaddend..Iadd. 46.The composition of claim 23 wherein said composition consistsessentially of particles at least about 97 percent of which are lessthan 0.05 microns in diameter after milling. .Iaddend..Iadd.
 47. Thecomposition of claim 23 wherein said composition may be represented bythe following formula:

    1.3 Na.sub.2 O.1.0 Al.sub.2 O.sub.3.1.2 MgO.14.3 SiO.sub.2.4.3 H.sub.2 O. .Iaddend..Iadd.
 48. The composition of claim 23 wherein said composition has a LOI in the range of from about 6.38 to 9.7% by weight; an oil absorption in the range of from about 108 to 170 cc/100 g; a surface area in the range of from about 59 to 176 M.sup.2 g; and a pigment (Elrepho) brightness of from about 90.4 to 94.5. .Iaddend..Iadd.
 49. The composition of claim 48 wherein said composition has a 325 screen residue of from about 0.04 to 5.3%. .Iaddend..Iadd.
 50. The composition of claim 49 wherein said composition has a Valley Abrasion of from about 1.5 to 10.9 mg. loss. .Iaddend..Iadd.
 51. The composition of claim 50 wherein said composition has a pour density of from about 8.6 to 12.0 lb./ft.sup.3. .Iaddend..Iadd.
 52. The composition of claim 51 wherein said composition has a pack density of from about 17.5 to 25.0 lb./ft.sup.3. .Iaddend..Iadd.
 53. The composition of claim 52 wherein said composition consists essentially of particles substantially all of which are less than 0.5 microns in diameter after milling. .Iaddend. .Iadd.
 54. The composition of claim 53 wherein said composition consists essentially of particles at least about 97 percent of which are less than 0.05 microns in diameter after milling. .Iaddend..Iadd.
 55. The composition of claim 54 wherein said composition has a TAPPI Brightness in fine paper of from about 87.1 to 90.2. .Iaddend..Iadd.
 56. The composition of claim 55 wherein said composition has a TAPPI Opacity in fine paper of from about 79.3 to 89.0. .Iaddend..Iadd.
 57. The composition of claim 56 wherein said composition has a percentage retention in fine paper of from about 42 to 57%. .Iaddend..Iadd.
 58. The composition of claim 57 wherein said composition has a 20% pH of from about 10.1 to 11.3. .Iaddend..Iadd.
 59. The composition of claim 58 wherein said composition has a percentage of solids in its wet cake of from about 23.6 to 29.7% solids. .Iaddend..Iadd.
 60. The composition of claim 59 wherein said alkaline earth metal is magnesium. .Iaddend..Iadd.
 61. The composition of claim 60 wherein said composition has an oil absorption in the range of from about 108 to 156 cc/100 g. .Iaddend. .Iadd.
 62. The composition of claim 61 wherein said composition may be represented by the following formula:

    1.3 Na.sub.2 O.1.0 Al.sub.2 O.sub.3.1.2 MgO.14.3 SiO.sub.2.4.3 H.sub.2 O. .Iaddend. .Iadd.
 63. The product of claim 23 wherein the product is produced by introducing a dilute aqueous solution of an alkali silicate and a dilute aqueous solution of an aluminum salt into an agitated aqueous receiving medium containing an alkaline earth metal salt or hydroxide, with at least some of the alkali silicate and aluminum salt solutions being simultaneously introduced into said receiving medium. .Iaddend..Iadd.
 64. The product of claim 63 wherein said aqueous receiving medium contains an alkaline earth metal salt and the pH of the reaction solution is maintained between about 8 and
 12. .Iaddend.